| ObjectivesTo determine dietary zinc absorption in Chinese elderly and provide the basic data for the setting of zinc RNI for China's elderly people.At the same time,to investigate the influence of marginal zinc deficiency on obesity and provide the theory basis for the study of the relationship between zinc nutrition and chronic diseases.In addition,to obtain preliminary specific expression proteins of individual zinc nutritional status with proteomics techniques and provide the foundation for the development of new detection targets or methods.MethodsIn the first part,twenty four 60 to 70 years old people from Hebei were recruited for this study and this study is 13 days.After 3 day adaptation period,3mg of 67Zn were administered with porridge and divided into three meals on the fourth day of test period.At the same time,the rare-earth element dysprosium(0.4 mg Dy per meal)was given along with isotope to check the completeness of the fecal samples.On the fourth day and the eleventh day,capsules of carmine red dye were given to subjects before breakfast to determine the initiation and end of feces collection.All the feces during the metabolic period were collected and a duplicate dietary sample was collected for 3 days.The samples were homogenized in a blender,freeze drying and powder was digested in a microwave oven.Total Zn contents of the samples were measured by atomic absorption spectrophotometern and Dy was analyzed by inductively coupled plasma mass spectrometry.The Zn isotope ratio was detected by multiplecollector inductively-coupled plasma mass spectrometry.The concentration of primary nutrients,energy and phytic acid in the food was examined by using the related routine protocols of the National Standard of the People's Republic of China.Calculated the apparent absorbance of zinc and corrected the value according to the recovery of dysprosium.Calculated the RNI of zinc.In the second part,thirty two adult male SD rats were randomly divided into four groups.Four groups were supplied different doses of zinc,low zinc group was fed with marginal zinc deficiency diet containing 6 mg/kg zinc,moderate zinc group was fed with 10 mg/kg zinc,pair-control group and control group were fed with normal zinc diet according to AIN-93M.All rats were sacrificed after 6 weeks.Serum,heart,liver,kidney,testis and adipose tissues were collected.Serum zinc,serum lipid,leptin,total antioxidant capacity(T-AOC),superoxide dismutase(SOD)and malondialdehyde(MDA)were detected.In the third part,one hundred and two SD rats were randomly divided into three groups.Three groups were supplied different doses of zinc,low zinc group was fed with marginal zinc deficiency diet containing 5 mg/kg zinc,pair-control group and control group were fed with normal zinc diet according to AIN-93G.All rats were sacrificed after 15 weeks.Serum and white blood cell were collected.According to the content of blood zinc,three serum samples were respectively selected from the 15th week and the 7th week low zinc group as the low zinc group and the middle zinc group,three serum samples were selected from the 15 week control group as the high zinc group,three isolated leukocyte samples were respectively selected from the low zinc group and the control group at the 15th week.After removing high abundance proteins from serum samples,the serum samples and white blood cell samples were quantitated,digested and iTRAQ reagent marked.All samples were identified by LC-MS/MS mass spectrometry and bioinformatics software was used to obtain the proteome information on rat serum and leukocyte from zinc deficiency rats.Results1.The mean(±SD)zinc intake from the representative Chinese diet was 10.6±1.5mg/d.The phytic acid-to-zinc molar ratio in the diet was 6.4.The apparent absorption rate of zinc using stable isotope technique in the elderly males and females subjects were 26.65 ± 6.81%and 22.52 ± 7.33%,respectively.The average recoveries of rare earth elements Dy were 86.96 ± 4.98%and 89.45 ± 6.61%,respectively.According to correcting the absorption rate with the recovery of dysprosium,the absorption rate of zinc was 30.84 ± 8.35%and 25.55 ± 9.14%,respectively.The Zn absorption rate for elderly males was categorized as high and for elderly females was moderate according to the WHO standards.The RNI for males and females were 10.4 mg/d and 9.2 mg/d,which was calculated by the absorption rate of zinc obtained in this experiment.2.From the 5th week,the serum zinc in low zinc group was significantly lower than that in low zinc pair-control group and control group(P<0.05).Low zinc group appeared symptoms of zinc deficiency,which aggravated with the prolongation of the time.Marginal zinc deficiency model was set up.At the 6th week,body fat ratio of rats in low zinc group was significantly higher than that in low zinc pair-control group and control group(P<0.05),body fat ratio of rats in moderate zinc group was significantly higher than that in low zinc pair-control group(P<0.05).The content of T-AOC and SOD in the liver and kidney of the low zinc group was significantly decreased(P<0.05),the content of MDA was significantly increased(P<0.05);the content of T-AOC and SOD in the liver of the moderate zinc group was significantly decreased(P<0.05),the content of MDA in the liver was significantly increased;the content of SOD in the kidney was significantly decreased(P<0.05).It indicated that the oxidative stress occurred in the low zinc group and the moderate zinc group,but different organs change characteristics of oxidation and antioxidant enzyme system was not same.3.From the 1th week,the serum zinc in low zinc group was significantly lower than that in low zinc pair-control group and control group(P<0.05).Low zinc group appeared symptoms of zinc deficiency,which aggravated with the prolongation of the time.Marginal zinc deficiency model was set up.In this study,205 and 3816 proteins were found in blood and white blood cell samples,64 were differential proteins in blood and 137 were differential proteins in white blood cell.The expression of 29 proteins in the blood and 16 proteins in white blood cells in low zinc group increased.The expression of 21 proteins in the blood and 121 proteins in white blood cells in low zinc group decreased.According to the analysis of pathway and network,the differential proteins in blood samples were involved in 9 metabolic pathways and 5 metabolic networks,and the differential proteins in leukocyte samples were involved in 17 metabolic pathways and 15 metabolic networks.Conclusion1.In this study,we firstly used stable isotope techniques to obtain the absorption rate of dietary zinc in Chinese elderly population.Our results found that the absorption rate of dietary zinc in Chinese elderly population was 27.86%,the absorption rate of zinc in the elderly males and females subjects were 30.84%and 25.55%,respectively.The absorption in men was higher than women.The current RNI in elderly female is lower than our calculation results.The elderly women may be at risk of Zn deficiency when use the current RNI.More attention is needed regarding elderly females' zinc status and health.2.Marginal zinc deficiency could lead to abnormal body fat and there was abnormal trend on body weight and blood lipids in this experiment,which indicates marginal zinc deficiency can increase the risk of obesity.The oxidative stress occurred in marginal zinc deficiency rats,but different organ oxidative damage characteristics were not same.Liver had a significant oxidative stress,kidney had a mild oxidative injury,heart and testicular damage occurred later.Increased oxidative damage in rats may be the main reason that marginal zinc deficiency increased the risk of obesity.Leptin levels reduced in zinc deficiency rats,which may lead to increase food intake,reduce energy consumption and accumulate fat in the body.It may be another reason for marginal zinc deficiency to increase the risk of obesity.Due to the limitation of the experiment time,marginal zinc deficiency on obesity and its mechanism remains to be further research,zinc supplementation on marginal zinc deficiency population may play an important role in the prevention and treatment of obesity.3.In this study,we used iTRAQ marker technique to study the comparative proteomics of serum and white blood cells in marginal zinc deficiency rats,which combined with multidimensional liquid chromatography and Q-Exactive mass spectrometry and obtained the whole proteome information with high-throughput protein identification.At the same time,with different zinc nutrition status of proteomic relative quantitative analysis,we found out the specific expression proteins on the evaluation of marginal zinc deficiency and established the corresponding proteome database which provised the foundation for the development of new detection targets or methods. |
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